This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Mutations in superoxide dismutase 1 (SOD1) cause familial amyotrophic lateral sclerosis (ALS). Expression of mutant SOD1 (SOD1G93A) in rats causes an ALS-like phenotype. Mutant SOD1 associates with mitochondria from the spinal cord, but not the liver. The proteins that mediate the interaction of SOD1 with mitochondria are unknown. We have immunoprecipitated SOD1 from spinal cord mitochondrial fractions and propose to identify proteins associated with SOD1 by mass spectrometry.